Do not under estimate the squirrel! He will hide from you as well as attack you, especially when their babies are threatened! They will reach thru a trap and slowly and completely remove all the bait, leaving you with an empty trap.
If you are fortunate enough to catch a mother squirrel, whose babies are in your attic, you will find the babies nearly impossible to catch. As it is in their genes to remain quiet when mom is gone and not to leave the nest. The squirrel can be very difficult!